This invention relates generally to contactors. More particularly, this invention relates to electronic actuation for mechanically held contactors.
Contactors, such as lighting contactors, are either electrically or mechanically held contactors used to control, for example, lighting in commercial and industrial applications. Today, a customer must purchase two different products, which are not easily interchangeable to serve both applications. Also, the manufacturer, distributor, and installer must inventory two different products for mechanically and electrically held applications. This drives significant manufacturing cost due to the reduced volume in each line, and cost of inventory. In addition, since the two products are dissimilar, they are not interchangeable in the field, increasing the cost of future retrofit.
To solve the above-described problem, some manufacturers provide an accessory that can be applied to a contactor to mechanically latch the contactor. Although this solves the problem, often the height of the contactor is significantly increased, because this design utilizes a second coil. The second coil also reduces the reliability of the design and adds to the cost and weight of the contactor.
The change of state in mechanically held contactor is normally done by pulsing its coil through a set of interlocking auxiliary contacts. The positioning of these auxiliary contacts is very critical, and can result in contactor malfunction if it is disturbed. Failure of the auxiliary contacts itself is yet another cause for malfunctioning of the contactor.
The switching device that does the pulsing function is yet another source for contactor malfunction. Bounce from the signaling switch, can result in chattering (kissing) on the contacts of the contactor, which can lead to increased arcing and welding of the contactor.
The cutting out of power to the coil of the mechanically held contactor is normally done when the travel of its plunger is almost complete (as the auxiliary contact are set to actuate at this position). If due to any malfunction, travel of the plunger is incomplete, then the auxiliary contactors do not get actuated. Then supply to the coil does not cut out, which results in the coil burnout.
A first known method for actuating a mechanically held contactor by electrical signals includes the use of two separate coils. The first coil being used for activating a plunger to close position and being held at the closed position by spring bias. Thereby the plunger stays in the closed position even if power to the first coil is removed. By activating the other coil (i.e. the second coil) spring bias is removed and the plunger is returned back to original position.
In a second known method, a single coil, which when activa ed pulls a plungert towards a center position with a follow through due to its momentum to the other side. The plunger is held on either side of the center position due to spring bias. Thus by using a single coil, transition from one spring biased state to another is achieved.
However, in both the above known methods, the supply to the coil is cut off through the activation of auxiliary contacts which is achieved by the motion of the plunger. These designs have the problems listed earlier.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by an electronic circuit connectable to a mechanically held contactor. In an exemplary embodiment of the invention, the circuit comprises a switch for providing an input signal, a controller for receiving the input signal and sending an output signal, and, a timing mechanism within the controller for setting a first period of time after receipt of the input signal and for setting a second period of time for limiting duration of the output signal, wherein the output signal is not sent from the controller until the first period of time is completed.
The above discussed and other drawbacks and deficiencies of the prior art are also overcome or alleviated by a contactor changeable in state from ON to OFF and from OFF to ON, the contactor comprising a pair of separable contacts, an assembly for separating and bringing together the pair of separable contacts, an energizable coil for moving the assembly in response to energization and de-energization of the coil, and, an electronic circuit mounted adjacent the coil, the electronic circuit including a timing mechanism for setting a predetermined time period for energization of the coil.
The above discussed and other drawbacks and deficiencies of the prior art are also overcome or alleviated by a method of utilizing an electronic circuit in a mechanical contactor, the method comprising initiating an input signal in the electronic circuit, receiving the input signal within a controller, waiting a first predetermined period of time for avoiding bounce from the input signal, at an end of the first predetermined period of time, sending an output signal from the controller for a duration lasting a second predetermined period of time, and, applying control power to a contact coil of the mechanical contactor during the second predetermined period of time.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.